1The American system of numeration for
denominations above one million was modeled on the French system but more
recently the French system has been changed to correspond to the German and
British systems. In the American system each of the denominations above 1,000
millions (the American billion) is 1,000 times the preceding one (one trillion =
1,000 billions; one quadrillion = 1,000 trillions). In the British system the
first denomination above 1,000 millions (the British milliard) is 1,000 times
the preceding one, but each of the denominations above 1,000 milliards (the
British billion) is 1,000,000 times the preceding one (one trillion = 1,000,000
billions; one quadrillion = 1,000,000 trillions).2For convenience in reading large numerals, the thousands, millions,
etc., are usually separated by commas (21,530; 1,155,465) or especially in
technical contexts by spaces (1 155 465). Serial numbers (as social security
numbers are usually written with hyphens (042-24-4705).